Ānandamaya

Ānandamaya-koṣa is the causal sheath (kāraṇa-śarīra) — the most subtle of the five koṣas. It manifests in suṣupti (deep sleep) as absence of suffering. It is NOT the absolute ānanda that is the nature of Brahman: it is only the koṣa in which the reflection of ānanda is clearest. Even ānandamaya-koṣa is an object (known by 'I slept well'), therefore not ātman. Investigation passes through it as through the others: neti-neti.